1. Technical Field of the Invention
The present invention relates to light irradiation onto an object to be measured.
2. Related Art
FIG. 4 shows an optical system of a conventional reflection measurement device which measures optical characteristics of a flat-shape sample. A description will now be given for the case where terahertz waves (electromagnetic waves having a frequency of 0.01 THz-10 THz) are measuring light, as an example. The terahertz waves output from a terahertz wave generator are reflected by an off-axial parabolic mirror, resulting in condensed terahertz waves. The terahertz waves are reflected by a flat surface mirror on the way, and are condensed on a sample surface. The terahertz waves reflected by the sample surface are again reflected by the flat surface mirror, are formed into collimated terahertz waves by an off-axis parabolic mirror, and are input into a terahertz detector.
For measuring the optical characteristics of a thin film or film as a sample, the measurement may be carried out while an incident angle θ of the measuring light entering the sample is changed. This is because, for example, the refractive index of the sample can be calculated highly precisely by acquiring the optical characteristics at various incident angles.
There is known a technique of irradiating a specimen with terahertz waves and detecting the reflected terahertz waves reflected by the respective layers (refer to the Abstract of JP 2012-237657 A, for example).